What to watch with CYP2D6 and fertility?

CYP2D6 is a key phase I drug-metabolizing enzyme, but direct evidence linking it to fertility is limited. Indirectly, CYP2D6 contributes to the metabolism of endogenous hormones like estrogen and progesterone, though other enzymes (CYP1A1, CYP3A4) play larger roles. The main clinical relevance lies in drug metabolism: fertility medications such as clomiphene (a selective estrogen receptor modulator) are partially metabolized by CYP2D6. Poor metabolizers may experience altered efficacy or increased side effects. Similarly, antidepressants (e.g., SSRIs) often prescribed during fertility treatment are CYP2D6 substrates. The evidence is primarily mechanistic and pharmacokinetic; robust prospective fertility studies are lacking. For clinical practice, knowing one's CYP2D6 phenotype can guide dosing of clomiphene or tamoxifen, but the impact on fertility per se is modest. Most fertility issues stem from hormonal, anatomical, or age-related factors. Be cautious of marketing claims that overstate CYP2D6's role in conception. A genetic test may be useful in personalized medicine contexts, but it is not a routine fertility diagnostic. Always consult a reproductive endocrinologist for comprehensive evaluation.